This invention generally relates to frame stacking systems for stacking large, assembled frames such as trusses for subsequent bundling and transport, and more particularly to a receiving stand for such frame stacking systems.
Prefabricated frames such as those used in housing construction are fabricated in various shapes and sizes. For example, a typical roof truss comprises truss components including a lower chord, angularly arranged upper chords and web members extending between and connecting the upper and lower chords. These trusses are generally fabricated at an assembly station in a horizontal orientation, such as by laying out the truss components on an assembly table and then connecting the elements to form the truss. Successive, similarly sized trusses are conveyed from the assembly station to a stacking station where the trusses are aligned and stacked together by a stacking system for subsequent bundling and transport to a construction site.
Some currently available stacking systems are configured for stacking prefabricated frames in a generally upright orientation. This stacking scheme has proven particularly useful in “peak-up stacking” of frames such as roof trusses wherein the trusses are stacked side-by-side in an upright orientation, with the peaks of the trusses pointed generally upward. For example, one such stacking system is offered by MiTek Industries, Inc. of St. Louis, Mo. under the tradename PEAK-UP STACKER. This stacking system comprises individual receiving stands spaced laterally from each other with their front ends positioned adjacent to a powered conveyor. Trusses are delivered by the conveyor to the stacking station in a generally horizontal orientation and then raised off of the conveyor by a lifting assembly to an upright orientation. Each receiving stand of the stacking system comprises a bench on which trusses are received in their upright orientation, and a stanchion extending up from the bench for supporting the trusses on the bench in their upright orientation. When a desired number of trusses has been stacked on the receiving stands, the trusses are banded together to form a truss bundle and the bundle is lifted up off of the bench by a fork-lift or other suitable lifting apparatus. Each stanchion is then manually pivoted relative to the respective bench to a lowered position away from the truss bundle to permit the truss bundle to be carried rearward away from the receiving stands by the fork-lift.
While such a stacking system has proven effective for stacking trusses in an upright orientation, repeated manual movement of the stanchions between their raised and lowered positions is often cumbersome and fatiguing for operators. The stanchions are about 14 feet in length and weigh more than 100 pounds apiece. Consequently, a substantial physical effort is required to lower each stanchion from its raised position to its lowered position in a controlled manner, and to subsequently lift the stanchion back up to its raised position for stacking another set of trusses on the receiving stands.
To this end, it is known to provide a counterweight at the lower end of the stanchion to gravitationally bias the stanchion toward its upright position. Thus, less effort is required by the operator to raise and lower the stanchion. However, because of the length of the stanchion, the counterweight be of substantial weight, such as more than 200 lbs. Adding such a large block of weight to the lower end of the stanchion renders the receiving stand bulky, extraordinarily heavy and difficult to manufacture.